The objective of this proposal is to elucidate the regulation and function of the NFAR proteins (for Nuclear Factors Associated with dsRNA). We have recently identified the NFARs as a substrates for the interferon-inducible, dsRNA-dependent protein kinase, PKR, a key receptor/inducer in dsRNA signaling and an important component in interferons response to viral infection and tumorigenesis. Recently, our laboratory has also demonstrated that activation of PKR leads to the transcriptional induction of pro-apoptotic molecules such as Fas and TNFR-1. Significantly, our preliminary data indicates that the NFARs may be novel histone acetyltransferases (HATS) and activators of transcription that are regulated by dsRNA. To further unravel the biological role of the NFARs in the cell, we propose the following: I. We will determine in vitro and in vivo, which regions of the NFAR protein are critical for its function as a HAT and transcriptional activator. We will also identify the promoter components responsible for mediating NFARs ability to regulate transcription. II. We have shown that the NFARs are efficient substrates for PKR. We will further examine the relationship of PKR and the NFARs and identify those sites critical for the interaction of these two proteins. The biological activity of NFAR variants defective in their ability to interact with PKR will be assessed in vitro and in vivo. III. To further evaluate, in vivo, the biological role of the NFAR proteins, we will establish cell-lines that controllably overexpress wild-type versions of the NFARs and compare them to cell-lines similarly expressing defective variants of these proteins. The role of the NFARs will be clarified by developing cell-lines and murine models that lack this gene. We anticipate that these studies will provide significant insight into the function and importance of the NFAR proteins and shed light into the mechanisms of PKR and interferon action, dsRNA signaling and the regulation of transcription in the cell.